Preparative liquid chromatograph systems (hereinafter referred to as a preparative LC system) have been known as systems which fractionate and collect a plurality of components contained in a liquid sample by use of a high-performance liquid chromatography (HPLC). A preparative LC system detects a sample component in an eluate when the eluate passes through a detector such as an ultraviolet-visible light absorption detector and controls preparative separation of the eluate in a fraction collector at a timing based on the detected signals. It generally takes a certain amount of time before the eluate arrives at a dispenser nozzle after passing through the detector. The delay time depends on the volume of flow channels from the detector to a tip end of the dispenser nozzle (hereinafter referred to as a delay volume), and flowing amount (flow rate) of a mobile phase. Therefore, in order to achieve accurate starting and ending of preparative separation of the target component in the fraction collector, it is necessary to precisely know the delay time, and is thus necessary to precisely obtain the delay volume.
A conventionally known preparative LC apparatus includes a means for allowing users to estimate the delay volume based on the inner diameter and the length of flow channels from an exit of a detector to the tip end of a dispenser nozzle, and to input numerical values of the delay volume. However, since such estimation sometimes includes errors, it is difficult to obtain the delay volume with high accuracy. Furthermore, an erroneous delay volume may be set due to human errors such as miscalculation by the user. Accordingly, it has been problematically difficult to accurately separate the component corresponding to a desired peak that appears in a chromatogram.
According to the preparative LC apparatus disclosed in Patent Document 1, a detector is provided on both the upstream and downstream sides of a fraction collector. Delay time in detecting the same component in the eluate between the two detectors is measured, and a delay volume is estimated based on the delay time. However, this method does not consider inner volumes of portions which are not included in the flow channel between the two detectors, such as channel-changing valves and dispenser nozzles, and thus problematically the calculated delay volume may not be sufficiently accurate. Further, disposing two detectors respectively on both the upstream and downstream sides of the fraction collector poses a problem of a complex structure.
The preparative LC apparatus disclosed in Patent Document 2 has a structure in which part of an eluent is branched through a splitter and a detector is provided. In the structure, another detector is positioned just prior to the fraction collector, and the delay time for a predetermined component in an eluate is measured using the detection results from the detector. Then, the delay volume is estimated from the delay time. However, similarly with the foregoing prior art, this method does not consider the volumes of a flow changing valve and a dispenser nozzle inside the fraction collector. Further, addition of another detector only for measuring the delay time leads to an increase in the production cost.    [Patent Document 1] U.S. Pat. No. 7,086,279    [Patent Document 2] U.S. Pat. No. 6,767,467